The invention relates generally to a prosthesis.
More particularly, the invention relates to an internal prosthesis for use when a joint loses the ability to perform pivotal movements.
The ability of a joint to perform rotational and/or pivotal movements is sometimes lost because of damage to or deterioration of the socket. In certain situations, the ability of the joint to perform such movements have be restored by implanting a bearing in the bone having the affected socket. The bearing then assumes the function of the socket. In many cases, however, deterioration of the bone prevents implantation of a bearing. For example, deterioration of the pelvis in the region of the hip joint may make it impossible to implant a standardized or specialized artificial socket or to reconstruct the natural socket by means of spongiosaplasty or synthetic osteological compounds. The installation of an internal prosthesis may not be possible when the natural socket cannot be reconstructed or replaced by an artificial socket.
In such situations, reconstruction operations such as, for instance, resection arthroplasty, may be performed. However, operations of this type do not yield entirely satisfactory results.
In the case of a hip joint, the so-called girdlestoneplasty may be used when the natural socket cannot be replaced or reconstructed. Here, the femur is pressed against the pelvis by means of straps. With this type of connection, positive engagement between the femur and the pelvis is achieved in a horizontal plane but not in the direction of force transmission between the pelvis and the femur. Consequently, undesired relative displacement of the pelvis and the femur may occur with attendant instability and pain.